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虽然上百万根的预应力混凝土桩已成功地应用于世界各地,但其设计仍然是凭借经验行事,以标称的规格确定轴向预应力及横向螺旋筋的数量和其分布形式,主要是选来能成功地担负吊装和锤击任务。近年来,一些露出地面的桩已发生不少垂直裂缝情况,这主要是由于热应变所引起的。在打桩中,横向裂缝情况也继续发生。有关地震对于打入层状土壤中的桩柱所引起的剪力和弯曲在理论上和试验方面的令人担心的影响,已为日本仙台地震的经历进一步证实。 轴向预应力钢筋及横向螺旋筋的合理设计能成功地避免这些问题,并能增加桩在地震下的韧性。 对于在打桩中产生的力素、应力和应变都作了描述和估算,并提出了钢筋的设计推荐。这样,只要设计出适合于具体工程需要的钢筋,在桩基中就完全可能并能以比较经济地实现高度的可靠性和有效性。
Although millions of prestressed concrete piles have been successfully used in all parts of the world, their design is still based on experience and the nominal specifications determine the number and distribution of axial prestressing and transverse spiraling tendons Selected to be able to successfully carry lifting and hammering task. In recent years, there have been many vertical cracks in some exposed piles, mainly due to thermal strain. In piling, horizontal cracks also continue to occur. The theoretical and experimental worrying effects of earthquakes on both shear and buckling induced into piles in layered soils have been further confirmed by the experience of the Sendai earthquake in Japan. Proper design of axial prestressing tendons and transverse tendons successfully avoids these problems and increases the pile’s toughness under earthquakes. The force, stress and strain in piling have been described and estimated, and the design recommendation of the reinforcement has been put forward. In this way, it is entirely possible and highly economical to achieve a high level of reliability and effectiveness in the pile as long as the rebar designed to meet the needs of a particular project is designed.